U.S. Pat. No. 2,785,198 discloses a process for producing polycarboxylic acids from bituminous coal, lignites, peat and the like or their carbonization product such as coal, tar, or pitch by thermal treatment with oxidizing agents such as nitric acid, chromic acid, permanganate, or oxygen or air under super-atmospheric pressure in an alkaline medium.
The crude oxidation product is subject to an extraction treatment with a polar organic solvent for both the monocyclic aromatic and high molecular weight polycarboxylic acids, and treating the thusly formed solution with water to extract the monocyclic aromatic polycarboxylic acids from the remainder of the mixture. The alkaline medium disclosed is sodium hydroxide.
U.S. Pat. No. 2,193,337 discloses a process for producing organic acids by heating carbonaceous material such as sawdust, wood chips, peat, or coal with oxygen-containing gases at elevated pressures and temperatures in the presence of at least 10 times the weight of the carbonaceous material of water and preferably an oxide or hydroxide of an alkali or alkaline earth metal. Oxalic acid and other organic acids which are formed, such as mellitic and benzoic acid or acetic acid, may be isolated from the resulting reaction mixture as salts of the alkali or alkaline earth metals. The caustic material disclosed is an oxide or hydroxide of an alkali metal or an alkaline earth metal and specifically lime, quick-lime, and caustic soda.
U.S. Pat. No. 2,786,074 discloses a process for making organic acids by oxidizing carbonaceous materials at elevated temperatures and pressures with gaseous oxygen in the presence of an alkaline solution. Alkalis which are suitable for use in a high pressure reactor are specified as sodium hydroxide, potassium hydroxide, and mixtures thereof.
U.S. Pat. No. 2,461,740 discloses a process for oxidizing carbonaceous material to aromatic acids using a two-stage oxidation process.
In the first stage, the carbonaceous material is oxidized to a state where it is soluble in aqueous alkali such, for example, as a solution of sodium hydroxide, potassium hydroxide, sodium carbonate, or potassium carbonate, especially at elevated temperatures.
Any acid or acid anhydride with suitable oxidizing properties which can be regenerated by air and recycled in the process can be employed, for example sulfur trioxide, oxides of nitrogen, or the acids formed by reaction of these compounds with water. Specifically disclosed are sulfur trioxide, N.sub.2 O.sub.3, and N.sub.2 O.sub.5.
In the second stage, U.S. Pat. No. 2,461,740 discloses the use of a high pressure elevated temperature reaction of oxygen gas in aqueous alkali. The aqueous alkali employed is a solution of sodium hydroxide, potassium hydroxide, sodium carbonate, or potassium carbonate.
U.S. Pat. No. 3,023,217 discloses a process for introducing carboxyl groups into aromatic compounds free from carboxyl groups, such as aromatic carbocyclic hydrocarbons and aromatic heterocyclic hydrocarbons. The patent discloses a process for introducing into aromatic carbocyclic or aromatic heterocyclic compounds free from carboxyl groups by reacting such materials in the absence of substantial amounts of oxygen, such as a non-oxidative atmosphere and under anhydrous conditions, with alkali metal salts of aliphatic carboxylic acids at elevated temperatures and pressures in the presence of catalysts. As disclosed in the process, it is necessary to exclude the presence of substantial quantities of oxygen. Examples of aliphatic carboxylic acids which are used in the form of their alkali metal salts, especially their potassium salts, are oxalic acid, malonic acid, maleic acid, and trichloroacetic acid.
Examples of suitable compounds free from carboxyl groups which may be used as starting materials for the process are aromatic carbocyclic compounds free from carboxyl groups such as monocyclic aromatic hydrocarbons such as benzene or its derivatives having saturated alkyl or cycloalkyl substitutes attached thereto, and dicyclic aromatic hydrocarbons such as naphthalenes, diphenyl, and other polycyclic aromatic hydrocarbon compounds. Similarly, aromatic heterocyclic compounds free from carboxyl groups which may be used as starting materials are heterocyclic compounds which contain one or more heteroatoms in the ring and which are designated as having an aromatic character because of their chemical behavior.
U.S. Pat. No. 2,948,750 discloses a process for carboxylating aromatic hydrocarbons by direct introduction of carbon dioxide to produce polycarboxylic acids.
Suitable starting materials which are disclosed are aromatic hydrocarbons, especially benzene but also toluene, xylene, cumene and diisopropyl benzene and other benzenes substituted with saturated or unsaturated alkyl or cycloalkyl radicals, naphthalene, diphenyl, diphenylmethane and other aromatic compounds which may also be substituted with hydrocarbon radicals.
Selective carboxylation is accomplished by heating the starting materials in the presence of an acid-binding agent, and carbon dioxide under anhydrous conditions. Examples of the acid-binding agent are carbonates of alkali metals, especially potassium carbonate, the salts of other weak acids such as bicarbonates, formates, or oxalates. Similarly, the corresponding compounds of other metals are suitable; for example, the carbonates of the alkali earth metals.
U.S. Pat. No. 3,023,216 discloses a method of introducing carboxyl groups into aromatic carbocyclic compounds free from carboxyl groups by reacting these compounds in a non-oxidative atmosphere with alkali metal salts of aromatic carbocyclic or aromatic heterocyclic carboxylic acids.
Suitable compounds which are free from carboxyl groups which may be used as starting compounds in this patent are similar to the starting compounds in U.S. Pat. No. 2,948,750.
U.S. Pat. No. 3,023,216 discloses reacting aromatic carboxylic compounds free from carboxyl groups with aromatic carboxylic acids in the form of their alkali metal salts.
Both U.S. Pat. Nos. 3,023,216 and 2,948,750 require specific chemical compounds as starting materials.
U.S. Pat. No. 2,833,816 discloses a process for oxidizing aromatic compounds using a catalyst comprising a lower aliphatic carboxylate salt of a heavy metal and bromine. Examples of a heavy metal are manganese, cobalt, nickel, chromium, vanadium, molybdenum, tungsten, tin, and cerium.
The metals may be supplied in the form of metal salts; for example such as manganese acetate. The bromine may be supplied as ionic bromine, or other bromine compounds soluble in the reaction medium such as potassium bromate.
Thus, the process requires the conjoint presence of bromine and a heavy metal oxidation catalyst.
The starting material required is an aromatic compound containing one or more aliphatic substituents to produce corresponding aromatic carboxylic acids.
U.S. Pat. No. 3,064,043 discloses a process for oxidizing para-toluic acid or para-formyl toluene to produce terephthalic acid.
U.S. Pat. No. 3,064,046 discloses a process for oxidizing toluic acid or formyl toluene to produce orthophthalic acid or isophthalic acid.
Both U.S. Pat. Nos. 3,064,043 and 3,064,046 require specific starting materials to be oxidized.
U.S. Pat. No. 3,558,458 discloses a process for preparing aromatic acids by treating an alkyl aryl ketone with water at an elevated temperature in the presence of a reaction promoting agent. The reaction promoting agent may comprise an alkaline catalyst, a transition metal salt, or actinic light. Examples of an alkaline catalyst include potassium acetate, lithium acetate, rubidium acetate, and cesium acetate. The process is conducted in water at a temperature of about 200.degree. to 400.degree. C.
The art discloses processes for the alkaline oxidation of coal employing large amounts of chemicals relative to the amount of water soluble coal acids prouced, see U.S. Pat. No. 2,786,074 and a report entitled "Producton of Chemicals by Oxidation of Coal", Battelle Laboratory, Columbus, Ohio of Mar. 31, 1975. The report also suggests the use of potassium acetate and acetic acid in a cyclic process for the Henkel reaction at page 19. The substance of the Battelle Report is incorporated herein by reference.
Recovery of caustic soda and sodium carbonate was disclosed by Industrial and Engineering Chemistry, Volume 44 (1952) at page 2791 in an article entitled "Water-Soluble Polycarboxylic Acids by Oxidation of Coal" beginning at page 2784.
Japanese patent disclosure 18,365 discloses the reclamation of alkali by recrystallization and requires the consumption of one part by weight of alkali and 1.5 parts of sulfuric acid for each two parts of coal consumed.
Non-alkaline oxidation of coal generally yields about 10 parts by weight of water soluble coal acids based on 100 parts of coal carbon consumed. Alkaline oxidation yields have been about 30 to about 42 parts per 100 parts of coal carbon consumed. Therefore, alkaline oxidation processes are favored because of the higher yield possible.
In systems like HCl/KCl, H.sub.2 SO.sub.4 /K.sub.2 SO.sub.4, and HNO.sub.3 /KNO.sub.3 the salts do not produce an alkali solution by hydrolysis because the acids involved are too strong. These systems over oxidize the coal and therefore result in much lower yield of coal acids.
Another disadvantage of treatment of coals with strong acids is the production of unwanted by-products by chlorination, sulfation, or nitration of the aromatic nuclei of the coal.
Coal acids have been prepared by nitric acid oxidation, U.S. Pat. Nos. 3,468,943; 3,709,931; 2,555,410; in the presence of nitrogen catalyst, U.S. Pat. No. 3,702,340; and oxidation in a non-alkaline aqueous medium, U.S. Pat. No. 3,259,650.
The caustic-oxygen treatment of coal has been described in U.S. Bureau of Mines Information Circular No. 8234 at pages 74 to 98.
In another process, U.S. Pat. No. 3,259,650 discloses the use of a non-alkaline medium and produces lower yields of water soluble coal acids.
U.S. Pat. No. 2,927,130 discloses a process for the recovery of alkalis and terephthalic acid from aqueous solutions containing alkali salts of terephthalic acid. Alkalis of interest are sodium, potassium and ammonium. The patent discloses that dialkali salts of terephthalic acid in aqueous solution can easily be divided into difficulty soluble monoalkali salts and alkali bicarbonate by introducing carbon dioxide into the solution, and that the difficulty soluble monoalkali salts of terephthalic acid can be hydrolyzed with water into free terephthalic acid and dialkali salts of terephthalic acid. The free terephthalic acid separates out as a solid, while the dialkali terephthalate remains in solution. U.S. Pat. No. 2,927,130 is incorporated herein by reference.
U.S. Pat. No. 2,819,300 discloses a process for oxidizing carbonaceous material with nitric acid, and then oxidizing the oxidation products produced from the nitric acid-carbonaceous material reaction with sulfuric acid to complete the oxidation to benzene carboxylic acids.
Although oxidation can be carried out in reclaimable acidic media, these processes are not as desirable because of lower yields and unwanted by-products due to chlorination, sulfation, and nitration.
The art discloses a process for preparing terephthalic acid by heating pure potassium phthalate, or pure potassium isophthalate, or pure potassium benzoate in the presence of catalyst such as cadmium, zinc and other metals, as reported in the Journal of American Chemical Society, Volume 79, pages 6005 to 6008.
The art also discloses a catalytic process for preparing terephthalic acid from toluene by oxidizing toluene to benzoic acid, reacting the thusly formed benzoic acid with potassium terephthalate in a methathesis reaction to produce terephthalic acid and potassium benzoate, and heating the thusly formed potassium benzoate in the presence of a catalyst to produce potassium terephthalate and benzene by a disproportionation reaction. Terephthalic acid and benzene are recovered and the thus formed potassium terephthalate is recycled to the methathesis reaction. The process is reviewed in Stanford Research Institute Report No. PEP'76-2-3 of Feb., 1977.
U.S. Pat. No. 3,215,735 discloses a process for treating a solution containing dialkali terephthalate and non-terephthalic acid as impurities with a reagent to adjust the pH of the solution so that terephthalic acid is in a soluble form while essentially all of the non-terephthalic acid is in an insoluble filterable form.
U.S. Pat. No. 3,579,572 discloses a process for the production of terephthalic acid which comprises treating an aqueous lithium or magnesium terephthalate solution with carbon dioxide under pressure, at a temperature between its solidification temperature and 80.degree. C., and separating the terephthalic acid which precipitates.
U.S. Pat. No. 3,766,258 discloses a process for the catalytic carboxylation of an alkali metal aromatic carboxylate to an acid containing at least one more carboxyl group.
U.S. Pat. No. 2,171,871 discloses that alkali metal derivatives of organic acid salts may be reacted with various reagents reactive with alkali metal organic compounds, e.g., carbon dioxide, sulfur dioxide or organic halides, to produce valuable products.
U.S. Pat. No. 2,176,348 discloses a process for preparing mellitic acid by a two-step oxidation of coal. The coal is first treated with a suitable oxidizing acid with or without the presence of a catalyst, followed by oxidation with an oxidizing salt such as alkaline permanganate.
U.S. Pat. No. 2,762,840 discloses that polycarboxy aromatic acids can be prepared by controlled oxidation with oxygen gas of an aqueous, alkaline suspension of bituminous coal.
U.S. Pat. No. 2,981,751 is directed toward a process for the oxidation of substituted aromatic compounds having at least one aliphatic, cycloaliphatic or partially oxidized aliphatic or cycloaliphatic substituent attached to the aromatic nucleus in the presence of an oxygen-containing gas and a calcined solid oxidation catalyst.
The substituted aromatic feed materials disclosed are toluene, butylbenzene, xylene, cumene, durene, dibutylbenzene, acetophenone, propiophenone, benzaldehyde, tolualdehyde, Tetralin, para-xylene, and cumene hydroperoxide. The oxidation is in the presence of a calcined solid oxidation catalyst which is derived by calcining an inorganic base having deposited thereon catalytic amount of a promoting metal component.
U.S. Pat. No. 3,529,020 discloses a process for oxidizing an organic material in the presence of a heavy metal crystalline aluminosilicate having uniform pores sufficiently large to permit entry of at least a portion of the organic material, and an oxidation initiator which is present in the pores. The heavy metal crystalline aluminosilicate acts as a catalyst.
The use of the applicant's invention allows reclamation of the reagent, higher yields, and less production of undesirable by-products. In the applicant's invention, the material principally consumed in the process is the aromatic material. Almost all other reagents are almost fully recoverable and completely reusable. In one embodiment of the applicant's invention, the applicant has found that 92 to 95 percent by weight of potassium could be recovered as potassium acetate.